Sen. Kent Conrad’s decision to retire in 2012 gives him one last chance to cement his legacy as a deficit hawk.

The North Dakota Democrat has long advocated for a sweeping, bipartisan budget deal that would pair politically painful spending cuts and tax increases to slash the deficit. He pushed to create last year’s bipartisan fiscal commission and, as one of its members, voted for its recommendation of $4 trillion in deficit reduction over the next decade.

Conrad said Tuesday that he had considered his decision for months and ultimately decided over the holidays that he wanted to focus his efforts on containing the national debt rather than running for another term.

“When I think about what has to be done for the country, I recognize that if we don’t get this debt under control, we are going to be diminished as a nation,” Conrad said in a Q-and-A on his website. “How do I want to spend my time in these next two years? I really want to be focused on helping getting a result on that great challenge.”

Conrad listed other priorities that he would like to focus on — including reducing dependence on foreign oil and writing a new farm bill — but his principal goal has always been tackling the debt.

The North Dakota Democrat announced his retirement once before — in 1992 — keeping true to a pledge that he wouldn’t seek re-election unless trade and budget deficits were reduced on his watch. But when Sen. Quentin Burdick died later that year, Democrats persuaded Conrad to run for Burdick’s seat.

Like the fiscal commission, Conrad wants tough new cost controls, but he wants to delay much of the pain until the economy is on sounder footing.

“You shouldn’t have the bite occur too soon or you endanger this fragile recovery,” he said at a Jan. 6 hearing with Federal Reserve Chairman Ben Bernanke.

Indeed, senior Democrats and Republicans are eyeing the new era of divided government as having at least the potential for a bipartisan debt deal like the 1997 balanced budget agreement President Bill Clinton struck with Republicans that led to years of surpluses.

Several choke points are coming up that will force the two parties to come together. A continuing resolution keeping the government operating expires March 4, and the $14.3 trillion debt ceiling must be raised soon afterward, with the deficit averaging about $100 billion a month. Some Republicans are demanding deep budget cuts in exchange for raising the debt ceiling and keeping the government open, and Conrad used the debt limit vote last year as leverage to get the fiscal commission off the ground.

One Senate Democratic aide likened Conrad’s newfound freedom to that exercised by former Sen. Chris Dodd (D-Conn.) during the negotiations over financial reform. Dodd was able to negotiate the overhaul — and get it passed — after he decided against running for re-election.

As Budget chairman, Conrad takes the lead in writing the Senate budget resolution and has pledged to work with his GOP counterpart, House Budget Chairman Paul Ryan (Wis.), to try to forge a deal. He will have to fight off liberals in his own party as well as conservatives to reach a consensus. Conrad’s support for trimming the cost of Social Security and Medicare and raising the retirement age have raised the hackles of some in his own party, and the commission proposal for a net tax increase has come under fire from Ryan and other conservatives.

Sen. Patty Murray is next in seniority on the Budget panel, but her office didn’t return an e-mail for comment on whether she would be interested in the chairmanship. The Washington Democrat also serves as Conference secretary and chairwoman of the Democratic Senatorial Campaign Committee.

Democratic leaders, meanwhile, could see a short-term benefit from Conrad’s decision to retire, even though it makes the Senate more likely to be in Republican hands two years hence: They’ll have one less vulnerable Member to protect on tough votes.

Republican aides have been eyeing the 23 Democratic seats up in 2012, including Conrad’s, as potential sources of Republican legislative victories in the next two years as they try to advance House GOP bills, noting that Senate Minority Leader Mitch McConnell (R-Ky.) said as much two weeks ago.

“How many of the 23 Democrats who are up in ’12 are going to be more interested in cooperating with us in trying to advance an agenda that’s going to come out of the House of Representatives that we think is going to be largely favored by the American people?” McConnell said.